Editing Harp seal (section)

====Thermoregulation====
[[File:Blanchon-idlm2006.jpg|thumb|left|Whitecoated pup]]
Harp seal [[Thermal insulation|insulation]] changes over the course of a seal's lifetime. Young harp seals rely on a lanugo [[pelt]] from nursing all the way up to their [[weaning]] age.<ref name="Pearson 501–511">{{Cite journal |last1=Pearson |first1=Linnea E. |last2=Weitzner |first2=Emma L. |last3=Burns |first3=Jennifer M. |last4=Hammill |first4=Mike O. |last5=Liwanag |first5=Heather E. M. |date=August 2019 |title=From ice to ocean: changes in the thermal function of harp seal pelt with ontogeny |url=http://link.springer.com/10.1007/s00360-019-01214-y |journal=Journal of Comparative Physiology B |language=en |volume=189 |issue=3–4 |pages=501–511 |doi=10.1007/s00360-019-01214-y |pmid=30923894 |s2cid=253890521 |issn=0174-1578|url-access=subscription }}</ref> The insulating quality of this fur depends on its ability to keep a layer of air trapped inside or between the hairs.<ref name="Kvadsheim 952–962">{{Cite journal |last1=Kvadsheim |first1=P. H. |last2=Aarseth |first2=J. J. |title=Thermal Function of Phocid Seal Fur |date=October 2002 |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1748-7692.2002.tb01084.x |journal=Marine Mammal Science |language=en |volume=18 |issue=4 |pages=952–962 |doi=10.1111/j.1748-7692.2002.tb01084.x |bibcode=2002MMamS..18..952K |issn=0824-0469|url-access=subscription }}</ref> It takes a year for their blubber to develop and for their first-year [[pelage]] to grow. This transition from thick [[lanugo]] fur to [[blubber]] is important because lanugo fur does not insulate well in water.<ref name="Pearson 501–511"/> Adult harp seals primarily use blubber for insulation.<ref name="Bioweb"/>

Harp seals combine [[anatomical]] and [[Ethology|behavioral]] approaches to managing their [[body temperature]]s, instead of elevating their [[metabolic rate]] and subsequently their energy requirements.<ref>{{cite journal |last1=Lavigne |first1=D. |last2=Innes |first2=S. |last3=Worthy |first3=G. |last4=Kovacs |first4=K. |last5=Schmitz |first5=O. |last6=Hickie |first6=J. |year=1986 |title=Metabolic rates of seals and whales |journal=Canadian Journal of Zoology |volume=64 |issue=2 |pages=279–284 |doi=10.1139/z86-047|bibcode=1986CaJZ...64..279L }}</ref> Their lower critical temperature is believed to be under {{convert|-10|C|abbr=on}} in air.<ref>{{Cite journal|last1=Boily|first1=Patrice|last2=Lavigne|first2=David M.|year=1996|title=Thermoregulation of juvenile grey seals, ''Halichoerus grypus'', in air|journal=Canadian Journal of Zoology|volume=74|issue=2|pages=201–208|doi=10.1139/z96-025|bibcode=1996CaJZ...74..201B |issn=0008-4301}}</ref> A thick coat of [[blubber]] insulates its body and provides energy when food is scarce or during [[fasting]].<ref name="Bioweb">{{Cite web|url=http://bioweb.uwlax.edu/bio203/s2012/lind_vale/adaptation.htm|title=Adaptation of the Harp Seal|website=bioweb.uwlax.edu|language=en-us|access-date=2018-04-03}}</ref> Blubber also [[wikt:streamline|streamline]]s its body for more efficient swimming. [[Brown fat]] warms [[blood]] as it returns from the body surface as well as providing energy, most importantly for newly weaned pups.<ref name="Perrin-2009" /> This blubber insulates the harp seal's core but does not insulate the flippers to the same extent. Instead, the flippers have circulatory adaptations to help prevent heat loss.<ref>{{Cite journal|last1=Kvadsheim|first1=P. H.|last2=Folkow|first2=L. P.|year=1997|title=Blubber and flipper heat transfer in harp seals|journal=Acta Physiologica Scandinavica|volume=161|issue=3|pages=385–395|doi=10.1046/j.1365-201x.1997.00235.x|pmid=9401592|issn=0001-6772}}</ref> [[Flipper (anatomy)|Flippers]] act as heat exchangers, warming or cooling the seal as needed. On ice, the seal can press its fore flippers to its body and its hind flippers together to reduce heat loss.<ref name="Perrin-2009" /> 

They can also redirect blood flow from the periphery to minimize heat loss;<ref name="Bioweb" /> the nostrils and eyes of harp seals are adapted to conserve heat, possessing a [[countercurrent heat exchange]] system and [[Rete mirabile|retia mirabile]], respectively.<ref>{{cite journal |last1=FOLKOW |first1=L. P. |last2=BLIX |first2=A. S. |last3=EIDE |first3=T. J. |title=Anatomical and functional aspects of the nasal mucosal and ophthalmic retia of phocid seals |journal=Zoology |date=November 1988 |volume=216 |issue=3 |pages=417–436 |doi=10.1111/j.1469-7998.1988.tb02439.x |url=https://zslpublications.onlinelibrary.wiley.com/doi/abs/10.1111/j.1469-7998.1988.tb02439.x |access-date=20 March 2025|url-access=subscription }}</ref>